1. Field of the Invention
The present invention relates to a charged particle beam writing apparatus, a write data creation method, and a charged particle beam writing method and, for example, relates to a method of creating new write data by reconfiguring write data used for electron beam writing.
2. Related Art
A lithography technique which leads development of micropatterning of a semiconductor device is a very important process for exclusively generating a pattern in semiconductor manufacturing processes. In recent years, with an increase in integration density of an LSI, a circuit line width required for semiconductor devices is getting smaller year by year. In order to form a desired circuit pattern on such a semiconductor device, a high-precision original pattern (also called a reticle or a mask) is necessary. In this case, an electron beam writing technique has an essentially excellent resolution, and is used in production of high-precision original patterns.
FIG. 7 is a conceptual diagram for explaining an operation of a variable-shaped electron beam writing apparatus. The variable-shaped electron beam (EB: Electron beam) writing apparatus operates as follows. An oblong, for example, rectangular opening 411 to shape an electron beam 330 is formed in a first aperture plate 410. A variable-shaped opening 421 to shape the electron beam 330 having passed through the opening 411 of the first aperture plate 410 into a desired oblong shape is formed in a second aperture plate 420. The electron beam 330 irradiated from a charged particle source 430 and having passed through the opening 411 of the first aperture plate 410 is deflected by a deflector, passes through a part of a variable-shaped opening 421 of the second aperture plate 420, and is shone on a target object 340 placed on a stage continuously moving in one predetermined direction (for example, an X direction). That is, an oblong shape which can pass through both the opening 411 of the first aperture plate 410 and the variable-shaped opening 421 of the second aperture plate 420 is written in a write region of the target object 340 placed on the stage continuously moving in the X direction. A scheme which causes an electron beam to pass through both the opening 411 of the first aperture plate 410 and the variable-shaped opening 421 of the second aperture plate 420 to form an arbitrary shape is called a variable-shaping scheme (VSB scheme).
With patterns increasingly finer in recent years, more precise and faster writing is demanded for electron beam writing. To deal with such circumstances, a method of ranking write patterns in the mask based on writing precision is proposed. According to such a method, main patterns requiring high precision and peripheral patterns for which low precision is enough are separated. Operation processing of write data is performed separately. Then, each pattern is written using write parameters in accordance with respective precision.
In such electron beam writing, on the other hand, if a mask coated with a resist is irradiated with an electron beam to write a pattern, a phenomenon called a proximity effect caused by back scattering by the electron beam that passes through the resist layer to reach a layer below the resist layer and then reenters the resist layer occurs. Dimensional fluctuations in which lines are written in dimensions deviating from desired dimensions when lines are written are thereby caused. Thus, various methods of correcting the proximity effect have conventionally been proposed. To correct the proximity effect of the applicable pattern, it is also necessary to consider patterns around the position thereof within the range of influence of the proximity effect.
If, as described above, an attempt is made to separate main patterns requiring high precision from peripheral patterns for which low precision is enough, when viewed from one pattern, a part of the other pattern may be contained within the range of influence of the proximity effect. In such a case, there is a problem that the proximity effect of main patterns cannot be corrected if main patterns and peripheral patterns are separated. As a result, dimensional precision of main patterns deteriorates.
Regarding the proximity effect correction, there is a method of operating the dose by changing values such as a base dose of the beam Dbase used for operating the dose and a proximity effect correction coefficient η to correct the proximity effect depending on the position (see, for example, Japanese Patent Application Laid-Open No. 2007-150243). However, if main patterns and peripheral patterns are separated, even according to such a method, it is difficult to solve the problem of becoming unable to correct the proximity effect of the main patterns.
As described above, even if main patterns requiring high precision and peripheral patterns for which low precision is enough should be separated, when viewed from one pattern, a part of the other pattern may be contained within the range of influence of the proximity effect. In such a case, there is a problem that the proximity effect of main patterns cannot be corrected if main patterns and peripheral patterns are separated. As a result, dimensional precision of main patterns deteriorates. However, conventionally, a method of solving the problem has not been established yet.